Bismuth Ferrite (BFO) is an intriguing material. At room temperature, it exhibits a canted antiferromagnetic order and ferroelectricity. In this material, the spin arrangement and the electric polarization are coupled. This allows the change of the magnetic order in the system by purely electrical means, thus promising ultra-efficient next-generation spintronic devices.
Peter Meisenheimer (University of California, Berkeley) and colleagues recently demonstrated the electrical switching of the magnetic textures in BFO. The spins in BFO are arranged as spin-cycloids, that is, they form superstructures spanning several unit cells.
Using Scanning NV Microscopy, the team was able to image these spin-cycloids in real space. They appear as wavy patterns, with a typical wavelength of around 100 nm.
The work was recently published in Nature Communications volume 15, Article number: 2903 (2024)
To influence these structures, a pair of electrodes was evaporated onto the material. By applying a large voltage, the BFO is exposed to an in-plane electrical field, which leads to ferroelectric switching. However, it is not clear by default in which state the spin cycloids will end up.
The combination of Piezo-force and Scanning NV microscopy on the Qnami ProteusQ allowed the researchers to conclude, that the system prioritizes certain states. This prioritization is understood as a consequence of the constraints imposed by the substrate. In other words, the magnetoelastic coupling leads to a selection of the spin cycloid vectors.
